Transmitter circuit



H. PAUl-l TRANSMITTER CIRCUIT Filed Auz. 12. 1926 2 Sheets-Sheet 1 pObserved animaba CurveI GurvolI '04-40-30 2o -lo o lo 2o :so 4o no w'*Pgr Nav. 1, 1927. 1,647,659 H. PAUL1 A TRANSMITTER CIRCUIT Filed111111.12. 192e 2 Sheets-sheet 2 Passes Nev; 1,1921. 1,647,659

UNITED .STATES PATENT OFFICE.Y

HEINRICH Panni, E EEEEIN, GERMANY, AssrGNoE rro s'iEiuENs a HaiesxEAx'riEN- GESELLSCHAFT, or siEiuENssrAD'r, NEAR BERLIN, GERMANY, aeEniraNcomrm.

TRANSMITTER GIRGUIT.Y Application illed August 12, 1926, Serial No.128,878, and in Germany August 12, 1925.

.'The invention relates to an adjustment rent and the pressure can beobtained by 55 between a transmitter and a consumer desuitably adjustingthe constants of these two vice, on which it acts (ohmic resistanceprireciprocal values representing the magnitude mary winding of arepeater), and the object of the resistances. l

is to transform without' distortion into elec- Withiiithe limits of thebeforementioned tric currents, the pressure variations actingapproximation, the relationship between r 60 on the transmitterdiaphragm (sound and p can be represented by a function hav-- waves).ing the form:

Figures 1 and 2 are curves relating to the A 1o invention while Figure aiuustretes the eir- (r-R) (riesig-:0; cuit. 65

In an article on transmitters (Elektrowhere R and P are the @o ordinatesof th technik and MaSChQeIlbeu, 1925, N0 13, middle point M, and a=MS ishalf the large page 239) R. Kelch glves QarbOn tiaIlSIIllttel axis ofthe equilateral hyperbola. R also curves for the current 1n relationshlpt0 represents the value ofthe resistance, which the pressure p on .thediaphragm, the bataccording t0 the approximate hyperbola, 70 terypressure V being steady. If the relavvould correspond to an infinitelygreat restionship of the transmitter resistance T to Sure p on thediaphragm (See Fig 2) ence the pressure p be ascertained from thesewithin the range of this approximation,

curves, 1t will be found that the function proximates very closely toone branch of an P "P Y elullatefal I lyebola h avlng lts asymptotes Ifthe transmitter bellocate'd in series with Pamueuy dlSPlCed Wlth respectt0 the? rec' the battery V and the consuming resistance tangularco-ordinate system 1', p. In Figure Ra, then he current s 1 the dottedline represents the curve for 80 r=f p obtained by xeiehs tests, whilethe V V full line curve is a branch of an equilateral Rl+r Ra +R +0hyperbola, which `approximates to the relap- F tionship between fl' andp when p=0 nearly. The approximate h erbola curves .ob

The example shows that this approximation is very good for many positiveand nega-tive gdlyalglyglfl bglstllgrpraxiez values of p. It is oftenfound to be a defective feature gllsvgspa cgil'tfuhat 1s to Say R has 35of the resistance transmitter that the sinoidal variations of itsresistance cause not only al oagslteealrlibbldtilii atil ilieitdiistflzigtresli: 9

5 e ternating currents of the same frequency,but ance, on which thetransmltter works, 1s

as:strattataastratte: ,ses wvluehof s essere 4o the relationship betweenresistance and curalsll a' magmtu e t al a rent is reciprocal value. Butin reality it is y of little importance whether the variations V P inthe resistance give rise to distortionless "'='(P )y transmittercurrents; but it is important that 45 the current shall closelycorrespond to the and the Pressu-re Variation A P have corre variationsin pressure on the diaphragm of SPOnding current Variations thetransmitter effected by the sound waves. V This result can be closelyachieved by mak- A'IFAP; ing use, of the beforementioned 4fact that 50there isa reciprocal relationship between the that is to say thevariations in the, current V pressure on the diaphragm and theresistbecome proportional to the pressure varia- 10b ance of thetransmitter. The following retions. 1 marks will show how a linear, thatis to say This holds good for the pressure varia- .y distortionless,relationship between the curtions within the range of the approximateance, on which the transmitter Works. Let

the voltage of the battery 11 be represented' ing tension across Ra isobtained when Ra=R, and

e RaAi= (lUgAp 144.530 4.5 volts.

' Ihe direct current transmitter current then 1s J=g(P) 111.1 X 10-aamps.

Hence very considerable undistorted amplitudes of current can beobtained by adjusting the 'consuming resistance according to theinvention.

In order to effect an adjustment in a transmitter circuit according tothe invention, it is first necessary to make tests to iind therelationship between the transmitter resistance r and the pressure p onthe diaphragm for a number of positive and negative values of p in theneighbourhood of 29:0. The constants R, P and C for the equilateralhyperbola which best approximates the tested relationship of the 1, pvalues in the neighborhood of p=0 then have to be determined,preferably, by calculation. The resistance Ra, on which the transmitterWorks, is then selected, according to the invention,

so that it equals the absolute value (negative) R, which has been foundaccording to the above method.

What is claimed is:

In a circuit arrangement for transmitters, a transmitter whoseresistance varies with the pressure on the diaphragm according to ahyperbolic function, said hyperbolic function approximating, for smallpositive and negative values of pressure, an equilateral hyperbola whoseasymptote corresponding to infinite pressure is displaced on theresistance axis of co-ordinatesin a negative direction from thecorresponding` asym tote of the first mentioned hyperbola, and a oad,having a resistance equal to the difference in the resistance ordinatesbetween said two asymptotes, connected to the transmitter' wherebyincrements in pressure cause proportional increments 1n current.

In witness whereof, I hereunto subscribeA of July A. D., 1926'.

